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Early Concepts of Evolution: Jean Baptiste Lamarck
Darwin was not the first
naturalist to propose
that species
changed over time into new species—that life, as we would say now,
evolves. In the eighteenth century, Buffon and other naturalists began
to introduce the idea that life might not have been fixed since creation.
By the end of the 1700s, paleontologists had swelled the fossil collections
of Europe, offering a picture of the past at odds with an unchanging natural
world. And in 1801, a French naturalist named Jean Baptiste Pierre Antoine
de Monet, Chevalier de Lamarck took a great conceptual step and proposed
a full-blown theory of evolution.
Lamarck started his scientific career as a botanist, but in 1793 he became
one of the founding professors of the Musee National d'Histoire Naturelle
as an expert on invertebrates. His work on classifying worms, spiders,
molluscs, and other boneless creatures was far ahead of his time.
Change through use and disuse
Lamarck was struck by the similarities of many of the animals he studied,
and was impressed too by the burgeoning fossil record. It led him to argue
that life was not fixed. When environments changed, organisms had to change
their behavior to survive. If they began to use an organ more than they
had in the past, it would increase in its lifetime. If a giraffe stretched
its neck for leaves, for example, a "nervous fluid" would flow
into its neck and make it longer. Its offspring would inherit the longer
neck, and continued stretching would make it longer still over several
generations. Meanwhile organs that organisms stopped using would shrink. |
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Lamarck believed that the long necks of giraffes evolved as generations of giraffes reached for ever
higher leaves. |
Organisms driven to greater complexity
This sort of evolution, for which Lamarck is most famous today, was only
one of two mechanisms he proposed. As organisms adapted to their surroundings,
nature also drove them inexorably upward from simple forms to increasingly
complex ones. Like Buffon, Lamarck believed that life had begun through
spontaneous generation. But he claimed that new primitive life forms sprang
up throughout the history of life; today's microbes were simply "the
new kids on the block."
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| Lamarck also proposed that organisms were driven from simple to increasingly more complex forms. |
Evolution by natural processes
Lamarck was mocked and attacked by Cuvier
and many other naturalists of
his day. While they questioned him on scientific grounds, many of them
were also disturbed by the theological implications of his work. Lamarck
was proposing that life took on its current form through natural processes,
not through miraculous interventions. For British naturalists in particular,
steeped as they were in natural theology, this was appalling. They believed
that nature was a reflection of God's benevolent design. To them,
it seemed Lamarck was claiming that it was the result of blind primal
forces. Shunned by the scientific community, Lamarck died in 1829 in poverty
and obscurity.
But the notion of evolution did not die with him. The French naturalist Geoffroy St. Hilaire would champion
another version of evolutionary change
in the 1820s, and the British writer Robert
Chambers would author a best-selling
argument for evolution in 1844: Vestiges of a Natural Creation.
And in 1859, Charles Darwin would publish the Origin of Species.
Different from Darwin
In many ways, Darwin's central argument is very different from Lamarck's.
Darwin did not accept an arrow of complexity driving through the history
of life. He argued that complexity evolved simply as a result of life
adapting to its local conditions from one generation to the next. He also
argued that species could go extinct rather than change into new forms.
But Darwin also relied on much the same evidence for evolution that Lamarck
did (such as vestigial
structures and
artificial
selection through breeding). And Darwin wrongly accepted that changes
acquired during an organism's lifetime could be passed on to its
offspring.
Lamarckian inheritance remained popular throughout the 1800s, in large
part because scientists did not yet understand how heredity works. With
the discovery of genes,
it was finally abandoned for the most part. But Lamarck, whom Darwin described
as "this justly celebrated naturalist," remains a major figure
in the history of biology for envisioning evolutionary change for the
first time.
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